Towards better description of solar activity variation in the International Reference Ionosphere topside ion composition model

• Published in: Advances in space research Vol. 55; no. 8; pp. 2099 - 2105
• Main Authors: Truhlik, V., Bilitza, D., Triskova, L.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15-04-2015
• Subjects: Density; Dynamical systems; Dynamics; Empirical model; Heat treatment; International Reference Ionosphere; Ion composition; Ionosphere; Mathematical models; Satellites; Solar activity; Topside ionosphere; International Reference Ionosphere; Solar activity; Topside ionosphere; Empirical model; Ion composition
• ISSN: 0273-1177; 1879-1948
• DOI: 10.1016/j.asr.2014.07.033

We present a revision of the ion composition model that is included in the International Reference Ionosphere (IRI) as the TTS-03 option. We employed a better description of the solar activity variation based on the assumption that the dependence of the logarithm of absolute densities of the individual ion species (H+, O+, He+ and N+) on the F10.7 index is linear. Unlike the TTS-03 model using the relative ion densities, the revised model employs absolute ion densities measured by the Atmosphere Explorer C&E and Intercosmos-24 satellites. Results of the revised ion composition model are presented, with special emphasis on the upper transition height (HT) during low solar activity. Equatorial HT produced by the model for a very low solar activity is ∼800km at daytime (14hLT) and ∼520km at nighttime (2hLT). These values are closer to HT observed by the Coupled Ion-Neutral Dynamics Investigations (CINDI) on the Communications/Navigation Outage Forecasting System (C/NOFS) satellite in the years 2008 and 2009 (minimum solar activity of the 23rd solar cycle) than the IRI-2007 and IRI-2012 options for the ion composition. A comparison of the options for the ion composition with the Sheffield University Plasmasphere-Ionosphere Model (SUPIM) is also shown.